In recent years, clinicians have turned their attention to a previously neglected group of patients who absorb a large proportion of our mental health resources. These patients suffer from chronic and debilitating deficits in their ability to function in today's complex society. However, with a few exceptions, little is known about the nature, cause or treatment of their disorders, known collectively as the Personality Disorders (PDS). In an important step toward rectifying this situation, the APA recognized the PDs as an independent domain of psychopathology in DSM-III. Extending the categorical approach used for classifying the major psychiatric syndromes, eleven PD diagnoses were specified. Their inclusion in DSN-III was hailed as a major conceptual advance over previous versions, yet many criticisms were also voiced. Among the most important of these was that a categorical system, which implies relatively discrete entities, is inappropriate for the PDs which contain many overlapping symptoms, and are not clearly distinct from normal functioning. An alternative that has been proposed, but not yet much researched, is a dimensional approach, which would allow assessment of the basic traits that characterize the domain of PDs. With this system, individuals would be rated on a number of important attributes rather than assigned to one or more diagnostic categories. The present study is among the first to investigate a dimensional scheme for assessing the domain of PDs. Phase One of the study consists of four steps: 1) clarification of those personality characteristics important for the PDs, 2) development of scales to measure each of the dimensions identified in Step One, both those in DSM-III and in other conceptualizations, 3) psychometric evaluation of the scales on a normative sample, and 4) pilot testing of the scales on a heterogeneous clinical sample. A planned Phase Two consists of extensive testing of clinical patients using both traditional methods of clinical diagnosis, such as structure interviews, and the scales developed in Phase One. This will permit direct comparison of the categorical and dimensional approaches to diagnoses of the PDs.